This webinar explores the intricacies and advancements in a well-known diagnostic tool; an EEG. An electroencephalogram – better known as an EEG – is a test that records electrical brain patterns from the scalp. EEGs are critical for the diagnosis of epilepsy and other neurological conditions. While this diagnostic tool has been available for nearly a century, there have been great advances in the portability and signal detection properties.
This webinar discusses how epilepsy patients have benefited from advances in EEG technology and the role of the EEG and other neuroimaging tools in the future of epilepsy diagnosis and seizure localization.
This webinar is presented by Dr. David Burdette, Epilepsy Section Chief for Spectrum Health Medical Group in Grand Rapids, Michigan. He has been at the forefront of EEG education having served on the American Board of EEG Technologists (ABRET) and the LAB-EEG board of the American Board of EEG Technologists (ABRET). Dr. Burdette’s clinical interests include neurotelemetry, long-term EEG trending, treatment of refractory epilepsy, treatment of status epilepticus, and electroencephalography.
Q&A Transcript
How often should a patient get an EEG if a past EEG was abnormal? At what point do you elect to have a 24 hour versus a 60-minute sleep-deprived EEG?
That is an interesting question, for which there’s not necessarily a right answer or a wrong answer. First, a question: why do people get EEGs? If someone has what I would consider a prototypical seizure…. The old expression goes, “If it walks like a duck and quacks like a duck, it’s probably a duck.” And if someone has seizures that walk and quack like seizures, it’s probably seizures. And if they walk and quack like a focal seizure (what we used to call a partial seizure), then I’m going to treat it as a partial seizure. I may not even need an EEG to do that.
I’ll get an EEG, just a one off type EEG, to make sure I’m not just totally out to lunch. But that EEG may end up being normal, even though that person is probably still have seizures. So, if a patient responds to the first medication I prescribe, as arguably 47% of people do, then that’s great. There is no compelling reason in my mind to repeat that EEG. If that person doesn’t respond to the first medication, I’ll usually have a plan B, so we’ll try the plan B. If that doesn’t work, I need more information.
I need to get some insight into how a person who hasn’t responded to the second medication is doing, so I may get a sleep deprived EEG or a two hour long EEG, so that way I can see those brain waves when they’re awake, drowsy, and asleep. Often times we need that sleep in order to really see the rhythmicity of the brain and for me to figure out, “Ah I was wrong. It was walking and quacking like a partial seizure, but in fact it was a generalized seizure and I chose the wrong medication.” Ideally that doesn’t happen, but it could. So, in that instance, I would get a sleep deprived EEG or I might get an ambulatory EEG so that over 24-48 hours, I can see that waking, drowsy sleep rhythmicity and see what’s going on.
If the individual still has seizures or the EEGs are unhelpful, then I will have the person come into the epilepsy monitoring unit. The place in the hospital where the healthiest people are, and we bring them in, it’s the one time in your life we want you to have a seizure, so we crash the person off their medications, sleep deprive them every other night, and ideally record a seizure.
That being said, in children there are many genetic forms of epilepsy which may appear in childhood and be outgrown later in life. In this case, serial EEGs are necessary to identify that progression.
Regarding the rhythms you showed at the end of the presentation, are those patterns in patients with epilepsy only or do healthy patients have similar multi-day rhythms?
There will be an element of speculation to my answer because we don’t know. But I don’t think it’s too much of a leap of faith to say that multi-day variation, the diurnal variation we tend to see in seizures, is being driven by a rhythm that is intrinsic to the brain itself. So in essence, the likelihood is that, seizures or no seizures, epilepsy or no epilepsy, we all have those rhythms. How they manifest though is difficult to say unless you have seizures.
Can you explain the subclinical seizures and EEG signatures called PLEDs, burst, and birds? This is a very detailed question about these different signatures.
Seizures are typically divided into “generalized seizures,” in which one second the brain is fine and then the next second both hemispheres are seizing, and “focal seizures,” in which seizures begin in a specific area of the brain. You’ve probably heard this notion that we only use ten percent of our brain. If we could use 90% we could do telekinesis, we could do whatever. Who knows, maybe people could develop telekinesis, I wouldn’t know. But I do know that we use our entire brains. A PET scan will light up the glucose metabolism the brain cells that are working, and we know that the whole brain lights up.
We’re using all of our brain, but we can only define what 10% of the brain does. When I do brain mapping on someone in anticipation of epilepsy surgery, in 90% of the parts of the brain I map, I can’t identify anything that happens when I stimulate it. Further, the person with epilepsy cannot identify that I’ve done anything. So, 10% of the brain is what we call “eloquent.”
If you have a seizure in eloquent cortex, it’s going to cause a symptom. If you have a seizure in a part of the brain that activates if you heard an oncoming train, then your seizure will cause an auditory hallucination of an oncoming train. But for other 90% of the brain, if the seizure starts there and stays focally there, then there’s a reasonable chance you’re going to have no symptoms. We would call that a “subclinical seizure.” In this case, we can see it on the EEG, particularly if we’re recording from directly within the brain itself. A seizure is happening, but it is subclinical – it’s causing no symptoms.
With PLEDs or LPEDs – we change the name sometimes but it’s the same phenomenon – this is a sign of an excited brain. If either some badness happens to the brain, a stroke for instance, then the area around the stroke will have excessive excitability. Or, if someone has known epilepsy and they go into status epilepticus – one seizure after another after another – the excitability of the brain really goes up in that area. The end result of this happening is that the brain keeps pushing toward a seizure, causing a burst of activity that shuts down that part of the brain for a second as it recovers, and then it happens again, boom, and then it shuts it down, and then boom…. Seizures during status epilepticus are periodic, like a metronome: fires, fires, fires, fires, it’s lateralized, it’s over one half of the brain, epileptic form discharges. So these are boom, boom, boom. This state is highly epileptogenic, but it is transient. So once you correct whatever is the underlying issue, it should resolve.
Bursts are a more descriptive term. In that case the brain is going about its business, then there’s a burst of activity, kind of like we saw earlier in my presentation where it’s burst, suppression, burst, suppression. So that is a descriptive term applied to any sudden outpouring of electrical activity within the brain. We will see bursts in a broad array of clinical situations from burst suppression to various epileptic or epilepsy related phenomena, and they are in essence this large outpouring of synchronous brain activity.
And then the final term, birds, has been applied in a few ways, but these are these brief, rhythmic discharges that are not quite seizures, but show a strong tendency towards seizures. This is a term most commonly used in neonatal EEGs. In adults, I see the brain waves going along, I see a burst of activity, looks like a spike, we call it a spike.
In the neonatal brain, development is happening really fast. Newborns get these spikes all the time and they can be normal. To differentiate abnormal bursts of activity, we use various terms to describe he specific kinds of spikes. If you see those spikes but they’re rhythmic and they last a certain period of time, then that is more worrisome for seizures. So that is most commonly how birds are used.
How sensitive are ambulatory EEGs? Is there a difference in the ability to pick up seizures between ambulatory versus in patient monitoring?
Ambulatory is more sensitive than a routine EEG. A routine EEG lasts 20 to 30 minutes. What are the odds that we’re going to pick up some abnormality in 20 to 30 minutes? It depends how active someone’s seizures are. If they’re having a seizure every five minutes, we’ll probably pick it up in a 30 minute EEG. Most people, however, are not having seizures as often as that. Most people have more widely dispersed seizures and therefore, by extension, more widely dispersed abnormal bursts of activity associated with seizures.
The longer we can record an EEG, the greater our likelihood of coming up with an answer to better inform our treatment options. A 20 to 30 minute EEG gives us some information. A 24 hour EEG gives us much more information, because we see those brainwaves in wakefulness, drowsiness, stages one, two, three, four, and REM sleep. The next step is being admitted to the epilepsy monitoring unit. If you go into an epilepsy monitoring unit and there are no medication changes made, you might as well have it done at home, because you’re less restricted at home.
But typically what we do in the epilepsy monitoring unit is evaluate situations when the ambulatory EEG didn’t give us the answers we needed. The in-patient epilepsy monitoring unit EEG allows us to take you off of medications, not necessarily to induce a seizure, but to remove your protection from seizures, so that we can record an actual seizure. That would be dangerous to do in many situations at home because there are risks of having multiple seizures. You could go into status epilepticus, you could (god forbid) have Sudden Unexpected Death from Epilepsy – it’s a scary situation. But in the hospital, it’s a monitored situation. An EEG tech is watching the screen 24-7 and when a seizure happens, they push a button, nurses come running, and they give medications to abort the seizure.
That’s the main difference – for an ambulatory EEG you’re probably on medication, and in the epilepsy monitoring unit we’re taking away the medication.
How do I know if my doctor knows the latest information about performing an EEG? Are there any questions I can ask?
I would ask if they have done an EEG or epilepsy fellowship. When someone goes into training in neurology, they do their internship right out of medical school. During that time, they get some basic training and learn more about treating patients with various maladies. Then they do a neurology residency, and focus on just brain-, spinal cord-, nerve-, and muscle-related issues. Part of that training is learning some basics of EEG, and learning the basics of taking care of a broad range of issues from Parkinson’s disease to tremors, to peripheral neuropathy to epilepsy.
Typically after someone develops seizures they will start with seeing a neurologist. And frankly, the majority of people do very well with seeing a neurologist. If, however, a person continues to have seizures, then it is time to move it up a notch. And that next notch takes the form of neurologists who did extra training for one or two years in either clinical neurophysiology, EEG, or in epilepsy (which also includes an EEG component). That by itself means that person is going to have a greater level of comfort and more in-depth knowledge of seizures and epilepsy.
In addition, you can check if your provider is board certified. Board certification will establish that a person has a minimal amount of knowledge. It doesn’t say that they’re the greatest thing since skim milk, but it assures to some degree a minimum level of competence. I tend to check if my doctor is board certified in the area in which I am seeking their opinion. That being said, some of the best epileptologists I know have never taken a board exam. Because you don’t have to take a board exam to practice in epilepsy.
If your seizures are well controlled, and by well controlled I mean you are seizure free, then your general neurologist is more than adequately capable of taking care of you. If you are still having seizures – once a month, a week, a day, a year – and adjustments are not effective, then it is time to seek the opinion of a specialist, who has done that extra training.
If that doesn’t work out, you kick it up a notch and you see someone who is in an NAEC level four epilepsy center. So that’s the National Association of Epilepsy Centers. They have a certification process whereby they evaluate who the epileptologists are, the neuropsychologists, the nurse practitioners, the entire epilepsy team, and determine if they have all of the credentials that indicate them to be highly competent in their field. If they do, those individuals will get a level three or level four (the highest level) designation. And if you’re having ongoing seizures and have tried multiple approaches, then ultimately you want to end up at an NAEC level four center.
The information contained herein is provided for general information only and does not offer medical advice or recommendations. Individuals should not rely on this information as a substitute for consultations with qualified healthcare professionals who are familiar with individual medical conditions and needs. CURE Epilepsy strongly recommends that care and treatment decisions related to epilepsy and any other medical condition be made in consultation with a patient’s physician or other qualified healthcare professionals who are familiar with the individual’s specific health situation.